Talk:Pendulum/Archive 1

acceleration
Art LaPella 23:30, Aug 26, 2004 (UTC)

Things that affect the period of a pendulum
Can someone add a little section about what affects the period of a pendulum? Like mass (which doesn't affect it) and amplitude and length of the string (which both do affect it). ~pie4all88

And info about horizontal pendulum and a link "horizontal pendulum" - redirect? Thanks very much. --Eleassar777 17:40, 18 Mar 2005 (UTC)

Clean energy source ?
as a viable 'clean' energy source, and if so, what would be the required dimensions of the pendulum? - 17.30 28:7:2005


 * No. I would have thought people understood the concept of a perpetual motion machine - and most importantly, why they don't exist. Fresheneesz 02:54, 27 May 2006 (UTC)

>> Rob TB >> Perpetual motion was indeed on my mind whe I suggested using the pendulum principle, although on reading the Wikipedia entry for "Perpetual motion machine" I realised I was talking more of a renewable energy source tapping into the earth's motion, rather than a perpetual motion machine in the true sense. Thanks for your reply, in any case, it was educational.

Lower gravity's affect on pendulums
I was wondering, if the motion of a pendulum is relavant to the gravitational force, what about ina vacum, would the laws still apply, even if you were floating in space. If you pushed the pendulum while holding the sting would it return, or come around in a cirlce? What about on lower gravitaional planets?


 * A vacuum has nothing to do with gravitation. If you mean in free fall (0-gravity), the formulas still apply. However, the period of the pendulum would go to infinity, and it would simply go around in a circle like you said. Fresheneesz 02:54, 27 May 2006 (UTC)

Newton's Discovery
Isaac_Newton discovered by experiment that the plane at which a pendulum moves changes over the course of 24 hours. Because of this, he confirmed that the Earth was spinning. He also saw that the pendulum moved faster at the Equator than closer to the North and South poles, since the Earth isn't perfectly spherical. 70.111.251.203 15:17, 28 February 2006 (UTC)
 * Perhaps you're thinking of the Focault pendulum? &mdash; RJH (talk) 20:29, 29 May 2007 (UTC)

Computing the period for angles greater than 10 degrees
Recall that:


 * $$T = 4\sqrt{\ell\over g}E\left({\sin\theta_0\over 2}, {\pi \over 2} \right)$$

where $$E(k,\phi)$$ is Legendre's elliptic function of the first kind


 * $$E(k,\phi) = \int^{\phi}_0 {1\over\sqrt{1-k^2\sin^2{\theta}}}d\theta$$

I changed the initial argument of Legendre's elliptic function in the applied example to $$\sin 10\over 2$$ because the result was incorrect. Initially the example read:


 * For example, the period of a 1m pendium at initial angle 20 degrees is $$4\sqrt{1\over g}E\left({\sin 10},{\pi\over2}\right) = 2.0102$$ seconds.

which is incorrect because $$\sin\left(10\right)$$ is not the same as $$\sin\left(20\right)\over 2$$ or $$\sin\left(10\right)\over 2$$.

The resulting equation and result $$4\sqrt{1\over g}E\left({\sin 10\over 2},{\pi\over2}\right) = 2.0102s $$ is now correct.

I also fixed the typo pendium to pendulum

--Teradon 04:00, 19 April 2006 (UTC)

This page is messy
This page isn't concise enough. It focuses much too much on derivations. I'm going to see if I can move the derivations to another page, and keep the bare equations here. Fresheneesz 02:54, 27 May 2006 (UTC)


 * Assuming the "simple pendulum" is a point mass is unnecessary, as we can use the concept of center of mass. Fresheneesz 03:27, 27 May 2006 (UTC)


 * This page doesn't even give general formulas like $$ \omega_o = \sqrt{m g l/I} $$. It ends by saying that either we have to use difficult integrals, messy functions, or by using approximations. I can't say for 100% certainty, but I'm pretty damn sure that there are equations that can easily find the period and other variables. For example, the equation I gave above.


 * This page is unencyclopedic and reads more like a textbook than any other page on wikipedia. This needs lots of fixing. Fresheneesz 04:10, 27 May 2006 (UTC)


 * But the formula $$ \omega_o = \sqrt{m g l/I} $$ is an approximation (for a physical pendulum, rather than a simple pendulum which seems to be the subject of this article). It only gives an accurate result when the angle of displacement is small and the approximation $$\sin\theta\approx\theta$$ can be used, as in the article. I agree though, that the original article was a bit too much. I think that it is fine now that it doesn't spend so much time deriving the equation, which is the purpose of a textbook and not an encyclopedia, and now is mostly about the approximate and exact methods of finding quantities related to the pendulum. Gershwinrb 04:31, 31 May 2006 (UTC)


 * Ah, well is there anywhere else on wikipedia that explains the formula I gave? It seems like a pretty basic-physics sort of thing. However, I still think this page needs lots of work. I only removed the first derivations, but the other two large sections are largely derivations as well, but I'd rather not sort through it myself. Anyone want to help? Fresheneesz 07:35, 31 May 2006 (UTC)

Maths
I've moved all the maths stuff to a new page, so that this page can remain clearer about what pendulums are and what they are used for. Tivedshambo (talk) 18:42, 12 July 2006 (UTC)


 * what did you call the new page?
 * BravoNovemberGolf (talk) 12:21, 25 March 2011 (UTC)

Amplitude
How come the formula for the period doesn't include the amplitude? The difference it makes is small, but it exists.


 * This has been addressed now. &mdash; RJH (talk) 20:28, 29 May 2007 (UTC)

From page
Revivalism During the second world war in Germany and Britain, occult practices and astrology, etc were utilised in the belief that they would benefit each side of the conflict, mainly by use in Germany and Britain. In Germany, the Germanic revivalism unit of the SS employed numerous astrologers and occultists. Three of the more well known mystisists used in the Third Reich by Walter Schellenberg through Heinrich Himmler, whom had a great deal of interest in Germanic mystisism and revivalism, were Ludwig Straniak (1879-1951), Dr. Wilhelm Gutberlet, whom both were pendulum users, and astrologer Wilhelm Wulff.

Adolf Hitler ordered the location finding and rescue of II Dude (Mussolini) by any means nessesary. This was done through the power of the pendulum as revealed in Peter Levenda's Unholy Alliance: "Nevertheless, a "Master of the Sidereal Pendulum" succeeded at last in locating Mussolini on an island west of Naples. To do this seer justice, it must be recorded that at the time Mussolini had no apparent contact with the outside world. It was, in fact, the island of Ponza to which he had been transferred at first. In other words, the "Master of the Sidereal Pendulum" had success- fully located the most famous Italian prisoner of the twentieth century ... and with no more than a decent meal, a few drinks, a good smoke, and a pendulum swinging over a map of Italy. It will be remembered that one of Hitler's closest friends was the "Master of the Sidereal Pendulum" Dr. Gutberlet. Whether or not it was this same "Master" who worked on the Mussolini problem is not revealed."

Architect Ludwig Straniak was also employed by the German military. He had a special gift for map pendulum dowsing. Straniak would dangle a pendulum over a given map and locate things. As a test, leaders of the German Navy requested him to locate the Pocket Battleship Prinz Eugen, then at sea. The Navy provided him with charts and were reportedly amazed that he had pinpointed the warship even through it was on a completely secret mission off of the coast of Norway. This impressed the Navy leaders enough to take the workings of the occult unit of the SS more seriously.

After the war Germany was demonised and the occult seen as a Nazi practise. Post 1945 German mystisism was virtually driven underground. Germanic spiritualism was revived to a large extent by Karl Spiesberger (Fratur Eratus) and by 1955 the Armanen runic system and Pendulum dowsing had once more become very much traditional in German speaking circles as it was before the war. Other notable German pendulum dowsers of which a great deal of pendulum material has been derived from are the works and practices of not on, but mainly Spiesberger and Straniak, are Dr. E. Clasen, Dr. K.E. Weiss (ß), Rud. Vöckler, Von Reichenbach, Professor Karl Bähr, Friedrich Kallenberg 1911-1934, Professor DR. Leopold Oelenheinz, and Professor Hellmut Wolff (30/3/1906-22/3/1986).  Leaving aside concerns about sourcing, I think this might go better at divination. Thoughts? Tom Harrison Talk 13:19, 27 September 2006 (UTC)


 * It needs to be written better I agree but this bit focuses on Pendulum use and not divination in general so I say keep it as a subsection of Pendulums for divination and dowsing. FK0071a 10:54, 29 September 2006 (UTC)

Plural
Is the plural pednulums or pendula? Neither m-w.com nor dictionary.com tell me. If pendulums is incorrect then Category:Pendulums will need to be moved. Cburnett 18:09, 10 November 2006 (UTC)


 * I've always seen it as pendula, and this is correct Latin grammar.
 * 71.193.96.115 03:02, 23 December 2006 (UTC)


 * The plural is pendulums - see Wiktionary entry or this page. – Tivedshambo (talk) 16:08, 2 January 2007 (UTC)


 * So why does the article use the rare or excessively pedantic false Latin plural?
 * I propose to change to the normal English plural if no-one objects.   D b f i r s   14:27, 25 April 2008 (UTC)

As long as we're on the topic of singular and plural, you should say "Neither THIS nor THAT tells me." A singular verb with a singular subject. Anyway, I suspect "pendula" is correct in Latin, but this article is in English. Michael Hardy 23:11, 2 January 2007 (UTC)
 * In any case, the Latin word is perpendiculum (or the adjective pendulus from which the neuter noun pendulum was later derived long after the days of Classical Latin), so "pendula" cannot be a correct original Latin form. At best it is an invented plural from the seventeenth century, pretending to be a Latin form.   D b f i r s   12:35, 18 July 2008 (UTC)

An Oddity?
This creates the expression m^2/s^2. I thought a period is a measurement of time it takes for one cycle (s, not m/s). Can someone help explain this? Sr13 05:25, 15 November 2006 (UTC)
 * L is measured in meters;
 * g is measured in m/s^2.
 * The square root of m^2/s^2 is m/s.

You just made a mistake with the maths:

length is in metres (m), acceleration in ms^-2

so: T -> (m/ms^-2)^1/2

Bringing s to the top of the equation:

(ms^2/m)^1/2

m cancels leaving (s^2)^1/2=s

Kelleycs01 17:30, 24 November 2006 (UTC)